The insight into separation of oleic, linoleic, and α-linolenic acid in peony seed oil from eutectic behaviors, polymorphic transition and solid-liquid phase equilibrium

Abstract

The melting crystallization is a crucial way to isolate unsaturated fatty acids from peony seed oil, mainly composed of oleic acid (OA), linoleic acid (LA), and α-linolenic acid (ALA). The solid-liquid phase behaviors of oleic/linoleic acid (OA-LA), oleic/α-linolenic acid (OA-ALA), and linoleic/α-linolenic acid (LA-ALA) binary systems at the cooling and melting stage were investigated by employing differential scanning calorimetry (DSC). The solid-liquid melting phase diagrams of the three binary systems were constructed by the thermal analysis and ideal liquidus lines simulated with thermodynamic models, which interpreted the eutectic behaviors, polymorphic transition, and intermolecular interaction in different binary systems. The eutectic behavior appeared in the OA-LA and OA-ALA binary systems at the OA concentration less than 40% and 20%, respectively, and in LA-ALA binary systems at any proportion. Based on the enthalpy of the three binary systems, the enthalpy plots and the melting Gibbs free energy were provided and predicted, respectively. This work provided insights into the separation of peony seed oil or other plants oil-based fatty acid mixtures, hence suggesting great potential for the optimization of crystallization technology.